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91.
Abbott JR Palmer GH Kegerreis KA Hetrick PF Howard CJ Hope JC Brown WC 《Journal of immunology (Baltimore, Md. : 1950)》2005,174(11):6702-6715
In humans and ruminants infected with Anaplasma, the major surface protein 2 (MSP2) is immunodominant. Numerous CD4(+) T cell epitopes in the hypervariable and conserved regions of MSP2 contribute to this immunodominance. Antigenic variation in MSP2 occurs throughout acute and persistent infection, and sequentially emerging variants are thought to be controlled by variant-specific Ab. This study tested the hypothesis that challenge of cattle with Anaplasma marginale expressing MSP2 variants to which the animals had been immunized, would stimulate variant epitope-specific recall CD4(+) T cell and IgG responses and organism clearance. MSP2-specific T lymphocyte responses, determined by IFN-gamma ELISPOT and proliferation assays, were strong before and for 3 wk postchallenge. Surprisingly, these responses became undetectable by the peak of rickettsemia, composed predominantly of organisms expressing the same MSP2 variants used for immunization. Immune responsiveness remained insignificant during subsequent persistent A. marginale infection up to 1 year. The suppressed response was specific for A. marginale, as responses to Clostridium vaccine Ag were consistently observed. CD4(+)CD25(+) T cells and cytokines IL-10 and TGF-beta1 did not increase after challenge. Furthermore, a suppressive effect of nonresponding cells was not observed. Lymphocyte proliferation and viability were lost in vitro in the presence of physiologically relevant numbers of A. marginale organisms. These results suggest that loss of memory T cell responses following A. marginale infection is due to a mechanism other than induction of T regulatory cells, such as peripheral deletion of MSP2-specific T cells. 相似文献
92.
International efforts to address climate change by reducing tropical deforestation increasingly rely on indigenous reserves as conservation units and indigenous peoples as strategic partners. Considered win-win situations where global conservation measures also contribute to cultural preservation, such alliances also frame indigenous peoples in diverse ecological settings with the responsibility to offset global carbon budgets through fire suppression based on the presumed positive value of non-alteration of tropical landscapes. Anthropogenic fire associated with indigenous ceremonial and collective hunting practices in the Neotropical savannas (cerrado) of Central Brazil is routinely represented in public and scientific conservation discourse as a cause of deforestation and increased CO2 emissions despite a lack of supporting evidence. We evaluate this claim for the Xavante people of Pimentel Barbosa Indigenous Reserve, Brazil. Building upon 23 years of longitudinal interdisciplinary research in the area, we used multi-temporal spatial analyses to compare land cover change under indigenous and agribusiness management over the last four decades (1973–2010) and quantify the contemporary Xavante burning regime contributing to observed patterns based on a four year sample at the end of this sequence (2007–2010). The overall proportion of deforested land remained stable inside the reserve (0.6%) but increased sharply outside (1.5% to 26.0%). Vegetation recovery occurred where reserve boundary adjustments transferred lands previously deforested by agribusiness to indigenous management. Periodic traditional burning by the Xavante had a large spatial distribution but repeated burning in consecutive years was restricted. Our results suggest a need to reassess overreaching conservation narratives about the purported destructiveness of indigenous anthropogenic fire in the cerrado. The real challenge to conservation in the fire-adapted cerrado biome is the long-term sustainability of indigenous lands and other tropical conservation islands increasingly subsumed by agribusiness expansion rather than the localized subsistence practices of indigenous and other traditional peoples. 相似文献
93.
Singaram?Gopalakrishnan Napo?KM?Cheung Bill?WP?Yip Doris?WT?AuEmail author 《Frontiers in zoology》2013,10(1):78
Introduction
Females having a longer telomere and lifespan than males have been documented in many animals. Such linkage however has never been reported in fish. Progressive shortening of telomere length is an important aging mechanism. Mounting in vitro evidence has shown that telomere shortening beyond a critical length triggered replicative senescence or cell death. Estrogen has been postulated as a key factor contributing to maintenance of telomere and sex-dependent longevity in animals. This postulation remains unproven due to the lack of a suitable animal system for testing. Here, we introduce a teleost model, the Japanese medaka Oryzias latipes, which shows promise for research into the molecular mechanism(s) controlling sex difference in aging.Results
Using the medaka, we demonstrate for the first time in teleost that (i) sex differences (female?>?male) in telomere length and longevity also exist in fish, and (ii) a natural, ‘menopause’-like decline of plasma estrogen was evident in females during aging. Estrogen levels significantly correlated with telomerase activity as well as telomere length in female organs (not in males), suggesting estrogen could modulate telomere length via telomerase activation in a sex -specific manner. A hypothetical in vivo ‘critical’ terminal restriction fragment (TRF, representing telomere) length of approximately 4 kb was deduced in medaka liver for prediction of organismal mortality, which is highly comparable with that for human cells. An age conversion model was also established to enable age translation between medaka (in months) and human (in years). These novel tools are useful for future research on comparative biology of aging using medaka.Conclusion
The striking similarity in estrogen profile between aging female O. latipes and women enables studying the influence of “postmenopausal” decline of estrogen on telomere and longevity without the need of invasive ovariectomy. Medaka fish is advantageous for studying the direct effect of increased estrogen on telomere length and longevity without the breast cancer complications reported in rodents. The findings strongly support the notion that O. latipes is a unique non-mammalian model for validation of estrogenic influence on telomere and longevity in vertebrates. This laboratory model fish is of potential significance for deciphering the ostensibly conserved mechanism(s) of sex-associated longevity in vertebrates.94.
95.
Escherichia coli has three DNA damage-inducible DNA polymerases: DNA polymerase II (Pol II), DNA polymerase IV (Pol IV), and DNA polymerase V (Pol V). While the in vivo function of Pol V is well understood, the precise roles of Pol IV and Pol II in DNA replication and repair are not as clear. Study of these polymerases has largely focused on their participation in the recovery of failed replication forks, translesion DNA synthesis, and origin-independent DNA replication. However, their roles in other repair and recombination pathways in E. coli have not been extensively examined. This study investigated how E. coli's inducible DNA polymerases and various DNA repair and recombination pathways function together to convey resistance to 4-nitroquinoline-1-oxide (NQO), a DNA damaging agent that produces replication blocking DNA base adducts. The data suggest that full resistance to this compound depends upon an intricate interplay among the activities of the inducible DNA polymerases and recombination. The data also suggest new relationships between the different pathways that process recombination intermediates. 相似文献
96.
The purpose of this paper is to validate a metabolic model describing the kinetics of tritium in man. The validation is based on measurements of background levels of loose and bound tritium in Italian subjects and their diets. Model predictions are compared with empirical measurements of tritium in human urine and tissue samples, and appear to be in close agreement. 相似文献
97.
The Kilham rat virus (RV) was found to vary in infectivity and antigenic characteristics when propagated in two different host systems. Both cross hemagglutination-inhibition (HI) and cross virus-neutralization tests revealed that a nonreciprocal or one way cross exists between RV propagated in rat embryo cell cultures (RE-RV) and RV propagated in suckling hamsters (H-RV). Specifically, immune serum to RE-RV inhibited hemagglutination and infectivity by both viruses to the same extent. Immune serum to H-RV, however, exhibited higher HI and neutralization titers to H-RV than to RE-RV. Infectivity studies demonstrated that, although both viruses were able to infect either host, the virus showed a higher infectivity titer for the last host in which it had been propagated. Serological studies indicated that H-RV possesses an antigen(s) not found on the RE-RV. This host-controlled variation did not result after a single passage in the new host, but rather required at least three passages for a complete conversion to occur, and did not appear to result from the incorporation of unaltered host antigens into the virus particle. Solubilization of purified RV propagated in each host with sodium dodecyl sulfate, 2-mercaptoethanol, and urea followed by electrophoresis in polyacrylamide gels indicated that the number of components in the protein of each virus was not the same. 相似文献
98.
M Morgan Conn Joe Kappock Dale Drueckhammer Richard Cammack Dennis Hall Tony Cass Jon D Stewart Graham RL Cousins Jeremy KM Sanders Sabine Flitsch Philip AS Lowden Richard Newman 《Current opinion in chemical biology》1999,3(6):631
A selection of interesting papers that were published in the two months before our press date in major journals most likely to report significant results in chemical biology. 相似文献
99.
KM Abha Mishra Runesh Podili Teja S. Pathlavath Kalyan K. Sethi 《Journal of biochemical and molecular toxicology》2023,37(8):e23409
Since the outbreak of highly virulent coronaviruses, significant interest was assessed to the brain and heart axis (BHA) in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-affected patients. The majority of clinical reports accounted for unusual symptoms associated with SARS-CoV-2 infections which are of the neurological type, such as headache, nausea, dysgeusia, anosmia, and cerebral infarction. The SARS-CoV-2 enters the cells through the angiotensin-converting enzyme (ACE-2) receptor. Patients with prior cardiovascular disease (CVD) have a higher risk of COVID-19 infection and it has related to various cardiovascular (CV) complications. Infected patients with pre-existing CVDs are also particularly exposed to critical health outcomes. Overall, COVID-19 affected patients admitted to intensive care units (ICU) and exposed to stressful environmental constraints, featured with a cluster of neurological and CV complications. In this review, we summarized the main contributions in the literature on how SARS-CoV-2 could interfere with the BHA and its role in affecting multiorgan disorders. Specifically, the central nervous system involvement, mainly in relation to CV alterations in COVID-19-affected patients, is considered. This review also emphasizes the biomarkers and therapy options for COVID-19 patients presenting with CV problems. 相似文献
100.
To support the Corrective-Measures and Cleanup-Alternatives Studies (CMS) prepared by Science Applications International Corporation (SAIC) at the Portsmouth Gaseous Diffusion Plant (PORTS) in Portsmouth, Ohio, a soil-leaching numerical analysis was conducted to help establish cleanup objectives for deep-soil contamination. For approximately 60 pollutants that exist at the PORTS site, the study defined those deep-soil concentrations that would most likely not cause groundwater contamination in excess of U.S. Environmental Protection Agency (USEPA) guidelines. These values were then used as the technical basis for defining soil-cleanup goals. Numerical modeling of environmental systems provides project managers with unique information that is not available from other sources. With its ability to quantify the important aspects of problem physics, modeling allows one to rapidly accumulate the physical insight needed to solve a problem in a systematic and focused manner. This increased understanding acquired early in the planning stages of a project permits managers to make decisions that are typically more thorough, cost effective, and defensible. This article describes one such numerical study conducted jointly by the Oak Ridge National Laboratory (ORNL) and SAIC for the PORTS. 相似文献